How do I perform multiple extrusions around a spiral?
You could use an array modifier to make a millipede, that way you don't have to mold all of the legs individually, but just once.

starting with a spiral (I used the AddCurve:Extra Objects add-on)





then create the base object:



Add an array modifier, set the fit type to Fit Curve and select the spiral as the curve object:



Add a Curve modifier and select the spiral as the object.



Select a few opposing faces on your face object and do Extrude Individual.
To shape the legs.



When you exit edit mode you should get something similar to this.

 

You could also add a new object to be used as the head



and select it to be used as the end of the array (maybe you could use a tail object as well, I don't know anything about entomology..)



The beauty of working with modifiers is that you can go back and edit the main object and reedit as much as you want and all of the instances on the array will be modifies as well. If you edit the spiral curve then all of the array will follow.





Adding an empty and using it as object offset on the Array modifier will allow you to scale it so the back of it is larger than the front.